Measuring instrument.



E. H. BRISTOL. MEASURING INSTRUMENT. APPLICATION FILED MAR. 3. 1913.

Patented (m. 29, 1918.

3 SHEETS-SHEET 3.

' index lifting device shown in Fig. 1;

111 sr area" orbs.

EDGAR H. BRISTOL, 0F FOXBORO, MASSACHUSETTS, ASSIGNOR, TO THE FOXBOROCOM- PANY, OF FOXBORO, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

. MEASURING IN STBUMEN T.

' Specification of Letters Patent.

Patented Get. 29, 1918..

To all whom. it may concern:

Be it known that I, EDGAR H. BRISTOL, a citizen of the United States,and a resident of F oxboro, in the county of Norfolk and Commonwealth ofMassachusetts, have invented an Improvement in Measurmg Instruments, ofwhich the following description, in connection with the accompanyingdrawings, is a specification, like char acters on the drawingsrepresenting like parts.

This invention relates to instruments for indicating and recordingpressures, temperatureand the like.

As shown herein, the invention is embodied in a pressure responsiveinstrument for indicating and recording differential pressures.

The character of the invention may be best understood by reference tothe following description of an, illustrative embodiment thereof shownin the accompanaying drawings, wherein:

Figure 1 is a front elevation of an illustrative gage embodying theinvention, with a portion of the. face of the gage broken away todisplay mechanism back of said face;

Fig. 2 is a side elevation of Fig. 1;

Fig. 3 on an enlarged scale is a detail of an Fig. 4 is a verticalsection taken on line 44 of Fig. 2;

Fig. 5 on an enlarged scale is a vertical sectlon through a part of thepressure responsive mechanism shown in Fig. 2; F Fig. 6 is a sectiontaken on line 66 of Fig. 7 on an enlarged scale is a signal device shownin Fig. 1;

Fig. 8 is a section taken on line 88 of Fig. 7;

Fig. 9 on an enlarged scale is a section taken on line 9-9 of Fig. 7;and

Fig. 10 is a detail of a shaft and bearing construction to be referredto.

Referring to the drawing, the illustrative instrument there shown asembodying the invention comprises a casing 1 (Figs. 1 and 2) in which isfixed a circular plate 3 adapted to receive and support a chart 5graduated radially to represent periods of time and circularly torepresent any desired plan of a pressures or other units or scales ofvalues, said chart being detachably secured to and rotated by ashaft 7driven by asuitable clock mechanism (not shown) contained in the saidcasing. An index or pointer shown herein as'a pen index 9 is movableover said chart and may be caused to travel in a generally radialdirection over said chart to in dicate or record thereon a pressureprevailing at or during any instant or period of time. The casing isprovided with a cover 10 hinged thereto and containing a glass throughwhich said chart and lndex are readily visible. 5 4

To control the movement of the index there is provided pressureresponsive means typified herein as an expansion tube 11. (Figs. 5 and6) composed of a series of expansible sections or diaphragms adapted tobe elongated or contracted by variation of pressure. An expansion tubeof the general character disclosed herein is shown in Letters Patent No.420,570 granted to W. H. Bristol February 4, 1890.

The tube 11 is mounted and inclosed Within a chamber formed by a casing13 having a flange 15 detachably secured to a base plate 17 by suitablescrews, said base plate in turn being secured to the rear face of thechart and clock containing casing 1 referred to. To support theexpansion tube within said caslng there is provided an elbow arm 19projecting laterally and upwardly from a? plug 21 threaded in anaperture in the plate 17.

Pressure may be admitted to the interior of the tube 11 by a pipe 23entered into the casing 1 and threaded to a union bracket 25 secured tothe rear wall of said casing. To conduct pressure thence to theexpansion tube 11 there is provided a small tube 27 1aving one endappropriately connected to said union and its opposite end connected tosaid plug 21. The tube supporting arm is provided with a bore 29communicating with the tube 27 and with the interior of the expansiontube 11.

ressure may be admit-ted to the interior of the casing 13 by a, pipe 31also connected to the union bracket 25 and connected by a small pipe 33with the interior of said casm To control the admission of fluid to thepipes 23 and 31 there may be provided a fitting 32 having passages andthree needle valves.

To transmit movements of the expansion tube to the index 9 referred to,there is pro vided an elongated shaft 35 (Figs. 6 and 10) contained inan elongated bearing 37 extending from within said expansion tube casinginto the chart and index containing casing. This bearing may be carriedby and extend through the elbow arm supporting plug 21 and be threadedthereto. Appropriate connections such as 39 may be provided forconnecting the expansion tube 11 to the shaft 35 for transmittingmovement from the former to the latter substantially as shown anddescribed in my copending applieation, Serial No. 741,193 filed January10,1913.

An important feature of the invention relates to the construction of theelongated bearing 37. In certain uses the difference in pressure in theexpansion tube 11 and casing 13 is extremely slight. .\s a result, thepresence of friction between the shaft 35 and its bearing 37 mayappreciably affect and prevent the faithful transmission of thedifferential pressure by the shaft to the index. To reduce the frictionbetween the shaft and its bearing to a minimum the bearing may comprisea thin shell 39 ot' brass or other suitable material having at one end aplug 41 separate from or integral with said tube as desired. This plugis provided with a bore corresponding to the diameter of the shaft. Thelong needle-like shaft 35 is of nickel or other suitable material. Thisshaft is introduced into the sleeve .39 with one end projecting throughthe plug 41. The other end is then centered within the sleeve by anysuitable device and the annular space formed between the shaft and theshell is filled by the pouring of molten tin or other suitable metalinto the open end of the shell. To prevent the adhesion of the shaft tothe tin the former may be given a coating of carbon in the form of sootor other lubricant as desired. The tin has a. lower melting point and issofter than either the steel shaft or the brass shell. As a result, itwill not injure either, but will fill the space between the shaft andsleeve and conform thereto. After the tin bearing filler has solidifiedthe shaft may be removed and the soot wiped therefrom. A hearing is thusproduced having a. conformity to the shaft and so fitting the latterthat the shaft may turn without play in its bearin but with a minimumfriction.

The pressure within the casing 13 is he quently very high although thedifferential pressure is small. This high pressure tends to cause theplate 17 to belly or bulge more or less. Since the shaft is offset fromthe center of the plate, this bulging would tend to cause the elongatedbearing 37 to tilt from a position perpendicular to said plate. Theexpansion tube supporting arm and the elongated shaft are connected atsubstantially the same point to the plug 21. As a result, any tilting ofthe shaft will be shared by a correspomling tilting of the arm and therewill be no relative displacement. of the tube and the shaft. This isimportant sincesuch displacementv might. tend to create a. rotativemovement of the shaft other than that caused by normal expansion andcontraction of the tube from differential pressures.

One end of the shaft'35 projects somewhat beyond the bearing 37 and maybe connected to a short shaft 43 by flexible arm connections 45 as shownin my said copending application. To connect this short shaft with theindex there is provided an arm 47 (Figs. 6, 7 and 8) projecting fromsaid shaft through an aperture 49 (Fig. 1) in the chart supporting plate3, referred to, and having a free end to which the index 9 is pivotallyconnected by a pin 51. Means is provided to permit the index to be.adjusted relatively to said arm in order that its are of travel mayparallel and conform to the radial graduations of 'the chart. To thisend the index is pivoted to the pin 51 at a point somewhat removed froman end of the index and an adjusting screw 53 is provided (Fig. 9)having a portion threaded in a nut 55 on a stud entered through said arm47 and a smooth portion occupying a bore in. a similar nut 57 carried bythe index. Interposed between said nuts 55 and 57 and encircling theadjustin screw is a spring 59 tending to slide the nut 57 along thescrew away from the nut 55. This movement is limited by a shoulder 61 onthe screw. To facilitate the adjustment of the screw it may have aknurled head 63. The turning of the screw 53 will cause the short arm ofthe index to be rocked relatively to its supporting arm 47 more or lessto vary the angle of the path of travel of the index pen. The spring 59maintains the arms in properrela tion without any lost motion.

To maintain equal pressures on opposite ends of the shaft 35 there maybe provided a goose neck tube 84 havin one end connected to the bearing37 and its opposite end entered inthe bearing carrying plug 21 toconnnunicate with the interiorof the casing 1 as shown in my saidcopending applie: tion.

An important feature of the construction shown relates to the provisionof means for supplying oil or other suitable lubricant to the elongatedshaft 35. To this end the bearing 37 is bored transversely as at 65(Fig. 10) at points on opposite sides of the point of connection of theshaft with the expansion tube connections. These bores are connected bypipes 67 (Fig. 6) with a duct 69 in the casing plate 17, referred to,said duct in turn being connected by a pipe 69 with an oil reservoir 71conveniently mounted on the rear of the casing 1. This reservoir may befilled through a neck at its top provided with an appropriate stopper73. The presence of pressure within the casing 13 acting on the exposedportion 75 (Fig. 10) of the shaft 35, would tend to oppose the feedingof the oil to the shaft. To equalize the pressure on the shaft at thispoint and the pressure on the surface of the oil supply there isprovided a pipe 77 in said reservoir extending above the surfacethereof, said pipe having a lower end communicating with a bore in theplate 17 parallelling the bore 69 referred to and communieating with theinterior of the casing 13 through a lateral inlet 7 9. By thisconstruction it will be apparent that'thesame pressure may be maintainedon the surface of the oil as exists within the casing 13. As a result,the oil may freely feed from the reservoir to the shaft as required andthereby continuously maintain the same properly lubricated. Thereservoir is of such size that it requires but infrequent filling sothat the shaft will'be properly oiled for long periods withoutattention. The maintenance of oil around the shaft has a furtheradvantage, in that it assists in preventing leakage between the shaftand its bearing. This construction is more fully described and isclaimed in my copending application Serial No. 212,556, filed Jan. 19,1918.

It is desirable to provide means for preventing an excessivedifferential pressure such as might expand or contract the pres sureresponsive tube 11 beyond its elastic limit. I will now describe adevice for automatically equalizing the pressures within the expansiontube and casing in the event that the differential pressure reaches apredetermined. limit. .This device comprises a casing 83 (Figs. 1, 2 and4) divided by a partition 85 into an upper chamber 87 and a lowerchamber 89. One end of the casing may be closed by a cap 91 threadedthereto. The chambers 87 and 89 contain mercury or other suitableliquid, the depth of. the mercury-in the upper chamber being preferablyconsiderably greater than the depth of the mercury in the lower chamber.

The expansion tube, pressure admission pipe 23 is provided with aT-union 101 (Fig. 2) to which is connected a pipe 95 having two branches97 and 99. The branch 97 extends through the top of the.casing 83 downinto the chamber 87 to within a short distance from the bottom of saidchamber, while the branch 99 extends through the chamber 87 and thepartition 85 and communicates with the lower chamber 89.

The casing, pressure admission pipe 31 is provided with a T-union 93connected by a pipe 103 with the upper chamber 87. The chambers areplaced in communication by a pipe 105 projecting above the liquid in theupper chamber 87 nearly to the top of the latter and projecting throughthe partition 85 down. a substantial distance beneath the level of theliquid in the lowerchamber 89 and nearly to the bottom of the latter.The depth of the liquid contained in the branch pipe 97 is proportionedto the range of pres sure indicating movement of the index 9. In orderto have a differential pressure it is necessary that the pressure in thetube should be greater than the pressure in the casing or vice. versa.For purposes of illustration it may be supposed that the pressure withinthe expansion tube is the higher pressure. In such case the branch pipe97 containing the column of liquid proportional to the range of movementof the index should be in communication with the high pressure expansiontube.

' In operation the greater pressure in the expansion tube will cause theliquid column within the. pipe 97 to fall and fluctuate in accordancewith the differential pressure. In the event that the differentialpressure is sufficient to overcome the column, the latter will be forcedby the pressure of the gas back of it down and entirely out of the pipe.Then the gas will be free to bubble up through the liquid contained inthe chamber 87 to the surface thereof and es-.

cape into the low pressure pipe 103 and thence escape to the responsivetube containing casing. This will automatically equalize the pressuresin said tube and casing and prevent the expansion of the tube beyond itselastic limit.

In preventing the contraction of the expansion tube beyond its elasticlimit, the pressure within the chamber is transmitted through the pipe103 into the space above a the liquid in the chamber 87 and thence downthrough the pipe 105 to the chamber 89. This will cause the liquidcontained in the lower end of the pipe 105 to fluctuate in accordancewith th differential pressure, but in the event that the pressure of thegas reaches a predetermined pointthe liquid will be forced down out ofthe pipe 105, thereby permitting the gas to bubble up through the liquidcontained in the chamber 89 and above the surface of said liquid. Thenceit escapes up through the pipe 99 to the expansion tube and as a resultequalizes the pressures within and without the tube and prevents unduecontraction of the tube.

The device described for equalizing the pressures when their differenceequals a predetermined amount is extremely simple in construction andoperation. One articular advantage thereof is that it is e ective inequalizing the pressures immediately on their reaching the predetermineddifi'erence. This is due to the fact that as soon as the liquid columnsare forced from the pipes 97 and 105 the gaseous fluid immediatelycommences to bubble up through the liquid in the chambers.

A feature of the invention relates to the provision of a signal or alarmfor a'uto matically calling attention to the predetermined pressures. Asshown herein, this device comprises a pair of divider-like arms 106(Figs. 1 and 7) having superposed ends pivoted on a bracket 109 on thechart supporting plate 3 referred to by screw 111. These arms areprovided with resilient contact fingers 113 having ends soldered orotherwise secured thereto and outer free ends projecting beyond the endsof said arms. Said fingers are limited in one direction-by stopshoulders 115 on said arms 106, but are free to yield and bend outwardlyaway from said shoulders on the engagement therewith of a pin 117projecting from the index 9. i

The arms 106 are provided at their pivot ends with conducting strips 119apertured to receive the fulcrum pin 107 and the bracket screws 111. Toinsulate one of the arms 106 and its conducting strip 119 from the otherarm and its conducting strip, the fulcrum pin 107 is incased in a sleeve121 (Fig. 8) of insulation material and said arms 106 are separated by awasher 123 of insulation material.

The index arm 47 is connected by a wire 1% (Fig. 7 with a battery 12701'other suitable source of electricity, said battery being connected. by awire 131 with a signal typified herein as an electric bell 133 althoughany other appropriate signal may-be used if desired. The bell isconnected by a wire 135 with one of the bracket screws 111 and by a wire137 with the other screw 11]..

When the index swings outward toward its limit of maximum pressure thepin 117 engages one of the contact fingers 113. This completes thecircuit and causes the bell to sound. When the index swings inwardtoward its limit of minimum pressure the pin 117 engages the othercontact finger 113 and again closes the circuit and causes the bell tosound. This notifies the attendant that an observation of the gageshould be made.

The contact carrying arms 106 are held in different positions ofadjustment by'the friction on their pivot and may be set to produce asignal at any limit desired.

The contact fingers 113 are light and freely flexible and offer butslight opposition to any excess movement of the index which may occurafter the sounding of the signal.

The contact carrying arms 106 may be set if desired to signal theautomatic equalizing of the pressures by the equalizing device or may beset to signal any other pressure desired.

In taking out and replacing harts from the gage it is necessary to liftthe index up from engagement with the chart. To do this automaticallythere may be provided an arm 125 (Figs. 1 and 3) having one end securedby a screw 127 to the chart carrying plate 3 and its other end portionbent up and arched as at 129 for engagement with the inner face of thecover glass. The arm is provided with a laterally projecting finger 131projecting radially toward the center of the chart beneath the index.When the casing cover 10 is closed the glass thereof depresses the arm125 from its dotted position to its full line position (Fig. 3) andlowersthe finger 131 out of engagement with the index. 011 the openingof the glass for the urpose of substituting a new chart for an o d onethe inherent resiliency of the arm 125 causes the same in the course ofthis opening movement to spring up to its dot ted position and engagethe index and lift the pen thereof out of contact with the chart. Thusthe index requires no attention in substituting new charts for old onesand both hands of the operator are free and available for manipulatinthe charts.

It will be an erstood that all of the features of the inventiondescribed herein need not necessarily be employed conjointly since someof them may be used separately to advantage. It will also be understoodthat the embodiment of the invention shown herein is selected forpurposes of illustration merely and is susceptible of variousmodifications within the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a device of the class described,- the combination of an index;responsive means for controlling the same; a casing for said responsivemeans; a plug entered in a wall of said casing and having an arm forsupporting said responsive means; means for conducting fluid pressuresto said responsive means and easing including a duct in said arm; andmeans to transmit movement from said responsive means through said plugto said index."

2. In a device of the class described,'the combination of an index;responsive means for controlling the same; a casing for said responsivemeans; a plug entered in a Wall of said casing; an arm projecting fromsaid plug for supporting said responsive means;

means to conduct fluid pressures to said responsive means and easingincluding a duct in said arm; means for transmitting movement from saidresponsive means to said index including a shaft and its bearing projecting through said plug; and a tube leadw necting said shaft to saidresponslve means;

and conduit means extending from said bearing through said plug forequalizing the pressure on the opposite ends of said shaft.

4. In a device of the class described, the combination of an index;responsive means for controlling the same; a casing for said responsivemeans; means to conduct fluid pressures to said responsive means andcasing; and means automatically tending to equalize said pressures on apredetermined difference between them, including means containing afluid column of an inherent pressure equal to said predetermineddifference.

5. In a device oft-he class described, the combination of an index;responsive means for governing the same; means independently to conductpressures to said responsive means; and means for automatically tendingto equalize said pressures when their difference attains a predeterminedamount including a casing having two liquid containing chambers; a pipeextending above the liquid in one and beneath the liquid in the other;means to conduct one of said pressures to one of said chambers; andmeans to conduct said other pressure to both of said chambers includinga tube containing a liquid column of a length proportionate to saidpredetermined difference.

6. In a device of the class described, the combination of an index;responsive means for governing the .same; means to conduct a pluralityof pressures to said responsive means; and means for automaticallytending to equalize said pressures on their exceeding a predetermineddifference ineluding a casing divided into an upper and a lower chamber;a pipe conveying one of said pressures to one of said chambers; pipesconveying said other pressure to both of said chambers; and a pipeconnecting said chambers having one end submerged beneath liquid in thelower chamber and its other end above the surface of liquid in the'upperchamber.

1 7. In a device of the vclass described, the combination of an index;responsive means for governing the same; a casing containing saidresponsive means; high and low pressure ducts for conducting pressuresto saidresponsive means and casing; and means for automatically tendingto equallze said pressures on their attaining a predetermined differenceincluding a casing divided into two chambers, one containing a liquiddeeper than the other; pipes communicating with said high pressure duet,one extending a distance beneath the surface of the deeper liquidproportional to said predetermined pressure difference and the otherleading into the chambercontaining the shallower liquid; a pipeconnecting the low pressure duct With the deep liquid chamber; and apipe connecting said chambers and having one end submerged beneath theshallow liquid and the other end projecting above the level of thedeeper liquid.

' 8. In a device of the class described, the combination of an index;responsive means; a casing for the latter; an element cooperating with awall of said casing; a fluid conducting arm projecting from saidelementforsupporting said responsive means; and means to transmitmovement fromsaid responsive means through said element to said index.

9. In a device of the class described, the combination of an index;responsive means for controlling the same; means for subjecting saidresponsive means to difierential pressures; and means including pressureresponsive liquid means for automatically tending to equalize saidpressures when the differential pressure reaches a predeterm'inedamount.

10. In a device of the class described, the combination of an index;responsive means for controlling the same; and means for subjecting saidresponsive means to diiferential pressures including high and low pres-Sure ducts, and means connecting said ducts containing a pressureresponsive liquid for automatically releasing the ditferentlal pressureto tend to equalize the pressures in said ducts when the diiferentialpressure reaches a predetermined limit.

11. In a device of the class described, the combination of an index;responsive means for controlling the same; and means for subjecting saidresponsive means to difl'erential pressures including high and lowpressure ducts, means tending to equal ze the pressures including meanscommunicating With said ducts and containing a pressure responsiveliquid of a sealing depth proportionate to a predetermined dlfferentlalpressure.

12. In a device of the class described, the combination of an index;responslve means for controlling the same; means for subjecting saidresponsive means to dlfi'erentlal pressures; and means for automaticallytending to equalize said pressures lncluding a pressure responsiveliqu1d havmg provlsion permitting the escape of the pressure fluidthrough said liquid to equalize the pressures when the difierentialpressure reaches a predetermined limit.

13. In a device of the class described, the combination of an index;responsive means 5 for controlling the same; means for subjecting saidresponsive means to differential pressures; and pressure responsiveliquid means having provision permitting said pressures to tend tobecome equalized immediately on their reaching a predetermineddiiference.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing Witnesses.

EDGAR H. BRISTOL.

WVitnesses HENRY T. VILLIAMS, LOUIS A. JoNEs.

